Alpha fetoprotein

Definition

Alpha fetoprotein (AFP) is a protein normally produced by the liver and yolk sac of a developing baby during pregnancy. AFP levels decrease soon after birth. AFP probably has no normal function in adults.

Alternative Names

How the test is performed

A blood sample is needed. For information on how this is done, see: Venipuncture

How to prepare for the test

There is no special preparation.

How the test will feel

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed

Your doctor may order this test to:

Screen for problems in the baby during pregnancy

Diagnose certain liver disorders

Screen for and monitor some cancers

During pregnancy, this AFP test can be done along with amniocentesis to help detect spina bifida or other birth defects in the developing baby.

Normal Values

The normal values in males or nonpregnant females is generally less than 40 micrograms/liter.

The examples above are common measurements for results of these tests. Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your doctor about the meaning of your specific test results.